Dyeing cellulose esters



VIII luv v| Patented Apr. 18, 1944 Search R()( DYEING CELLULOSE ESTERSRobert Schnegg, Dormagen, Germany; vested in the Alien PropertyCustodian N Drawing.

Original application May 24, 1939,

Serial No. 275,399. Divided and this application September 27, 1940,Serial No. 358,667. In Germany May 28, 1938 Claims.

The present invention relates to the art of dyeing cellulose esters, andmore especially, to a process for dyeing shaped articles like fibres,films, bands, and so on of highly acetylated cellulose, i. e. celluloseacetate having an acetate content of above 59%; such cellulose acetatesare for the most part soluble in chloroform.

It is known that highly esterified cellulose acetate is not easily dyedeven with such dyestufis which are usually employed in dyeing the lowercellulose acetates. The same holds true when trying to increase theaffinity of highly esterified cellulose acetate towards other dyestuffclasses, for instance, acid wool dyestuffs by animalizlng. This greatresistance of highly esterified cellulose acetate to all kinds ofdyestuffs is presumably due to the fact that the articles manufacturedtherefrom possess a rather horny surface free of pores which would allowthe dyestuil. panticles, which are mostly high molecular, to wander intothe interior.

It is known that similar difliculties, but on a lesser scale, areencountered when dyeing common acetate artificial silk which is lesshighly esterified and is soluble, not in chloroform, but in acetone, andthat it has been tried to overcome the difiiculties by adding certainswelling agents to the dye-baths for such artificial silk.

However, when trying to apply the processes used in dyeingacetone-soluble acetate artificial silk to the problem in question, theresult is not successful. It was rather unexpected, therefore, when Ifound that nevertheless also articles from highly esterified celluloseacetate can be very easily dyed when the articles are previously broughtinto a highly swollen condition and are dyed in this state. In order toachieve this result, I have found it to be necessary to treat thearticles with at least 40% aqueous acetic acid or a swelling agent of atleast equal swell ing action; furthermore, it is preferable to carry outthis swelling treatment at high temperatures, for instance, temperaturesof above 50 C. It may be noted that under such conditions the commonacetone-soluble artificial silk is completely dissolved or at leastdestroyed to an extremely high degree. Contrary thereto, the mechanicalproperties of the articles of highly esterified cellulose acetate, forinstance, resistance to break and elongation at break, are practicallyunimpaired by the present process.

After the treatment with one of the swelling agents, the articles can bedyed directly in deep and full shades; the dyeings so obtained have goodfastness properties. It is especially possible to dye animalizedarticles after the said swelling treatment with acid wool dyestuffs andto obtain dyeings of excellent fastness. Before dyeing, the swellingagent may be removed from the articles by washing with water, withoutpractically losing the property of being easily dyed. This property isonly lost when the articles are dried before dyeing.

I have now furthermore found that by a suitable treatment it is evenpossible to dry the articles having been treated with one of the abovestrong swelling agents in a manner that they retain the property ofbeing easily dyed. In order to achieve this result, I treat the articleswhich have been brought into the strongly swollen condition, if desiredafter removal of the swelling agent by washing, with a fixing agentselected from the group consisting of aqueous solutions of salts ororganic or inorganic acids and wetting agents, which are free fromsulphonic acid groups; these fixing agents may be employed alone or inadmixture with each other. Apparently by this treatment the swollencondition of the cellulose acetate articles which is necessary for theirbeing easily dyed is fixed to some extent. After the said fixingtreatment the articles may be dried. They remain easily dyeablethereafter and may be stored for any length of time or shipped to thecustomer without being impaired with regard to their dyeing properties.If before or during dyeing the fixing agents are washed out from thearticles, the cellulose acetate will again pass into the unswollen statewhereby the dyestuff particles are very strongly fixed in the interiorof the material so that the dyeings produced in this way show excellentfastness properties. For instance, dyeings with acid wool dyestuffs onanimalized cellulose material having been produced according to myinvention are faster in many respects, for instance, against fulling andwashing than the same dyeings on wool. As I have mentioned in severalinstances, the process according to my invention is of special value indyeing animalized material of highly esterifiecl cellulose acetate withacid wool dyestufis. Such material is produced in known manner, forinstance, by incorporating basic substances like nitrogen bases with thematerial, for instance, by adding a suitable nitrogen base to a spinningsolution for artificial fibres from highly acetylated cellulose. It ispossible in this way, for example, to prepare artificial fibres fromcellulose having an acetate content of above 59% which can be 'dyedalone or together with wool in equal shades as wool. For example,cellulose triacetate fibres are prepared which contain a basic nitrogencontaining resin, the fibres are treated with at least 40% aqueousacetic acid or a swelling agent of similar strength, are then treatedwith one of the above mentioned fixing agents and thereupon dyed with anacid wool dyestuff. The fibres may then be worked up into a mixed fabrictogether with wool and, by aftertreating with the same dyestuif, may beuniformly dyed. It is self-understood that in a similar way two-coloredeffects may be produced. It is furthermore possible to work upanimalized cellulose triacetate fibres together with wool to slivers,yarns, skeins, fabrics and so on, and to treat these materials with aswelling agent which will not impair the wool. Thereupon the materialsmay be dyed in one or the same bath in uniform shades with acid wooldyestuffs. As above mentioned the fastness of the dyeings on thecellulose acetate articles surpasses that of the same dyeings on wool,especially as regards the fastness to washing and fulling.

Of course the process is also applicable to textile printing. Forinstance, a fabric from cellulose triacetate fibres or animalizedcellulose triacetate fibres may be printed with one of the above strongswelling agents and thereupon may be dyed with a suitable dyestuif, ifdesired, after having been treated with one of the said fixing agents.In both cases dyed patterns on a white ground or vice versa may beobtained.

Example 1 Fibres which have been prepared from chloroform-solublecellulose acetate (acetate content: 59-61%) according to a wet-spinningprocess are continuously passed through a bath containing 60% aqueousacetic acid. The fibres swell strongly. Thereupon the fibre bundle isdeacidified by washing with water and dyed with a water insolublecellulose acetate dyestuff. By using, for instance, Cellit Fast Blue B(Schultz, Dyestuffs Tables, 1st suppl. vol., 1934, page 75), a deep blueshade is obtained whereas without the said swelling treatment the fibresare practically not dyed.

When trying to treat common acetate artificial silk (acetate content:54-55%) in the same way, the fibres are completely dissolved.

Example 2 Fibres swollen and washed as described in Example 1 are cutinto staples and brought into a bath containing -30% of an inorganic ororganic salt. The following salts, if their solubility permits so, maybe used: chlorides, bromides, iodides, sulfates, nitrates, borates,phosphates, sulfites, thiosulfates, thiocyanates of the alkali andalkaline-earth metals, furthermore, alkali and alkaline-earth metalsalts of the lower fatty acids, and mixtures of the said salts. Afterthe swollen fibres have been treated for 5-10 minutes in a salt bath,for instance, a solution of common salt, they are centrifuged and dried.After shortly washing the fibres are dyed as usual with celluloseacetate dyestuffs, for instance, Celliton Fast Black BTN (Schultz,Dyestuif Tables, lst-suppl. vol., 1934, page 76). Contrary to theuntreated fibres, they are dyed in deep and full shades.

The usual softening and finishing agents may be added to the salt bath.

Example 3 Instead of a salt bath as described in the foregoing example,there may be used an aqueous solution of 5-50 g. per litre of a wettingagent which is free from sulphonic acid groups, for instance, a reactionproduct of a reactive tertiary amine with the anhydride of a substitutedsuccinic acid, or a condensation product of oleyl alcohol or of castoroil with an excess of ethylene oxide.

Example 4 Fibres having been subjected to a swelling treatment asdescribed in Example 1 are aftertreated with a bath containing 2-10% ofa salt and 0.050.5% of wetting agent which is free of sulphonic acidgroups. The results are similar to those obtained according to Example1-3.

Example 5 Cellulose acetate artificial silk (acetate content: 59%)prepared by a dry spinning process is treated in skein form for 15-120seconds at a temperature of 30 C. in a 50% aqueous acetic acid. Afterhaving been washed with water, the silk is dyed with Celliton Fast BlackBTN in a deep black shade, whereas the untreated silk is hardly dyed. Ofcourse, it is possible to add an aftertreatment of the swollen fibres asdescribed in Examples 24.

Example 6 To a raw solution of cellulose triacetate, there are added545% (calculated on cellulose acetate) of a reaction product of starchbenzene sulfonate with an amine as described in the application Ser. No.180,157, filed December 16, 1937, and the solution is spun into fibres.In spite of the presence of the nitrogenous compounds, these fibres arebut scarcely dyed with acid wool dyestuffs.

The fibres are then continuously passed through a bath containing 60%aqueous acetic acid at a temperature of 20 C. for 15-120 seconds,thereupon washed with water and are dyed, while still wet, with acidwool dyestuffs, for instance, Amido Yellow E (Schultz, Dyestuffs Tables,vol. 1, 1931, No. 16). The deep dyeings obtained in this manner areespecially distinguished by their fastness. For example, the fastnessagainst fulling is 4-5 (Normen der Deutschen Echtheitskommission 1935),whereas a corresponding dyeing on wool has a fastness against fulling of1-2. A series of other acid wool dyestuffs act in the same way, forinstance, Quinoline Yellow (Schultz, Dyestuffs Tables, vol. I, 1931, No.918, Brilliant Crocein B (Schultz, Dyestuff Tables, 1st suppl., vol.,1934, No. 539), Alizarine Rubinol R (Schultz, Dyestuff Tables, vol. I,1931, No. 1210), Wool Fast Violet B (Schultz, Dyestuif Tables, vol. I,1931, No. 974), Alizarine Direct Blue A (Schultz, Dyestuif Tables, vol.II, 1932, page 9), A20 Acid Black 3 BL special (Schultz, DyestulfTables, 1st suppl. vol., 1934, page and so on.

Example 7 A solution of cellulose triacetate in glacial acetic acid ismixed with an animalizing agent, for instance, a reaction product ofchlorinated paraffin with ethylene diamine, and is spun by thewetspinning process; the fibres obtained therefrom are swollen in a 60%aqueous acetic acid at 60 C. for 15 seconds washed with water, andtreated for 5 minutes in a salt bath containing 5% sodium acetate, 2%ammonium thiocyanate, 2% of a finishing agent and 0.5%isododecenyl-succinic acid-diethyl amino-methyl ester. The centrifugedand dried fibre is excellently dyed by acid wool dyestuffs.

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vmluv VII Example 8 A fibre bundle of cellulose triacetate beinganimalized as described in Example 6 is swollen for 30 seconds at atemperature of C. in a 65% aqueous acetic acid which contains about 2%of a chromium compound, for instance, sodium bichromate or chromiumacetate and, if desired, a reduction agent like formaldehyde or glucose.The bundle is freed from acid and cut into staples. The fibres areafter-treated in a salt bath (containing 8% sodium acetate, 1% of awetting agent free of sulfo groups and 2% of a usual preparation), driedand worked up with wool to a yarn or textile fabric. The mixture isuniformly dyed with acid wool dyestuffs. Especially suitable arechromable dyestuffs. The dyeings on the artificial fibres are not onlyof the same fastness to washing, fulllng and perspiration, but are equalto the dyeings on pure wool regarding the fastness to light.

Example 9 Triacetate artificial silk containing an animalizing agent isworked up with wool in the relative proportion 1:1. The mixture istreated in a bath containing 60% aqueous acetic acid and 2% glucose forseconds at C., centrifuged, washed and dyed in the wet state with wooldyestuffs such as, for example, Anthralane Blue B (Schultz, DyestuffTables 1st suppL, vol., 1934, page 68). The dyeings obtained are uniformon both kinds of fibres. Dyeings of particular fastness are obtained byusing salts of the acid sulfuric acid esters of leuco vat dyes, whichalso dye both kinds of fibres equally and with the same fastnessproperties.

Example 10 On working as described in Example 9, but inserting, afterthe swelling, a salt treatment, similar dyeings are obtained as those ofExample 9.

Example 11 A fibre produced as described in Example 8 is dyed with awater-insoluble cellulose acetate dyestuff, for instance, a CellitonFast Dyestuff. By the presence of the animalizing substance, theafiinity of the triacetate against such dyestuffs is not as one shouldhave believed, diminished, but even considerably increased, so that, forinstance, the dye baths are almost completely exhausted and the dyeingsare deeper than on acetate artificial silk having an acetic acid contentof 54-55%.

Example 12 Fibres of chloroform-soluble cellulose acetate produced bythe dryor wet-spinning process are locally printed with 60% aqueousacetic acid, if desired, in the presence of a thickenin agent andthereupon dyed, or treated with salt and after drying dyed withcellulose acetate dyestuffs at 70-80 C. Thereby fibres are obtainedwhich show interesting two-colour effects, because the untreated placesdo not or practically not absorb the dyestuff, whereas the treatedfibres absorb the same very strongly.

Example 13 Fibres of triacetate having incorporated therewith ananimalizing agent are spun and treated as described in Example 12.Flamed fibres may be obtained with cellulose acetate dyestuffs or withacid wool dyestuffs, chrome dyestuffs and so on.

Example 14 A fabric prepared of cellulose triacetate fibres is printedin patterns with a paste containing 65% aqueous acetic acid, washed anddyed, or washed, treated with a salt as described in Example 7 and thendyed. With suitable dyestuffs, for instance, with Cellit Fast Blue B,dark patterns on a white ground are obtained.

Example 15 A fabric of triacetate artificial silk having incorporated ananimalizing agent is printed as described in Example 14. On dyeing withcellulose acetate dyestuffs, similar effects as in Example 14 areobtained. By dyeing with acid wool dyestuffs or with chrome dyestuffswhich reserve acetate silk, coloured patterns on a white ground areobtained.

This application is a divisional of application Ser. No. 275,399, nowPatent No. 2,328,682.

I claim:

1. A process for improving articles of cellulose acetate having anacetate content of at least 59 per cent, which comprises treating thearticles with aqueous acetic acid of at least 40 per cent strength, as aswelling agent, treating the swollen articles with an aqueous solutionof a wetting agent comprising the reaction product of an excess ofethylene oxide upon an alcohol selected from the class consisting ofoleyl alcohol and castor oil, to fix the swollen condition of thearticles, and drying the articles.

2. A process for improving articles of cellulose acetate having anacetate content of at least 59 per cent, which comprises treating thearticles with aqueous acetic acid of at least 40 per cent strength, as aswelling agent, treating the swollen articles with an aqueous solutionof a wetting agent containing about 5 to 50 grams per liter of thereaction product of an excess of ethylene oxide upon an alcohol selectedfrom the class consisting of oleyl alcohol and castor oil to fix theswollen condition of the articles, and drying the articles.

3. A process for improving articles of chloroform-soluble celluloseacetate having an acetate content of 59 to 61 per cent, which comprisestreating the articles with aqueous acetic acid of 60 per cent strength,as a swelling agent, treating the swollen articles with an aqueoussolution of a wetting agent comprising the reaction product of an excessof ethylene oxide upon an alcohol selected from the class consisting ofoleyl alcohol and castor oil to fix the swollen condition of thearticles, and drying the articles.

4. The process as defined in claim 1 wherein the wetting agent comprisesthe reaction product of an excess of ethylene oxide upon oleyl alcohol.

5. The process as defined in claim 1 wherein the wetting agent comprisesthe reaction product of an excess of ethylene oxide upon castor oil.

ROBERT SCHNEGG.

